The present invention relates generally to agricultural round balers for forming round bales of cut crop material and twine wrapping systems that automatically wrap the formed bales with twine before expelling them onto a field for subsequent handling. More particularly, the invention relates to an improved twine wrapping mechanism that dispenses multiple twine strands and allows selective twine spacing adjustment in order to reduce the time required complete the twine wrapping operation.
Typical round balers (also referred to simply as a “baler”), such as disclosed in U.S. Pat. No. 6,209,450 to Naaktgeboren et al., are agricultural machines that pick up a cut crop material from the ground and form it into a compacted round bale in a bale forming chamber. When the bale has been sufficiently compacted to a desired density or a desired size depending on the baler construction, bale density or bale size sensors, as appropriate, send signals to a controller that subsequently sends a signal to an operator's panel to stop forward motion of the baler so that a bale wrapping operation can be performed, wherein the formed bale is wrapped with netting or twine to produce a completed wrapped bale.
Typically, the wrapping operation is performed by a bale wrapping mechanism having a twine wrapping arm which traverses the length of the rotating bale while dispensing one or more strands of twine. When a wrap cycle is initiated, the arm is moved arcuately to an extended or insert position with an end of the twine strand dangles from the end of the twine arm sufficiently close to the rotating bale so that the end of the twine strand is adjacent to the bale. Subsequently, the dangling strand is caught by the cut crop material of the rotating bale as it rotates in the bale forming chamber so that the twine is pulled into the bale forming chamber and wrapped around the bale. As twine is pulled from the twine arm and wraps about the rotating bale, the arm is rotated so that the arm end from which the twine is dispensed traverses an arcuate path and dispenses twine along the length of the bale so that twine is helically wrapped around the bale along substantially its entire length. At the end of a wrap cycle, one or more wraps secure the twine end to the bale. Before the completed wrapped bale is expelled from the baler, the twine strand is cut, the baler tailgate opens and the completed wrapped bale is then expelled from the baler to the ground.
In order to reduce the time necessary to complete the wrapping operation, it is known to provide a bale wrapping apparatus having a twine arm mechanism for simultaneously dispensing two twine strands along spaced-apart paths. Due to the typically arcuate path of the twine arm, the spacing between the twine strands will vary as the arm sweeps through its movement path, generally resulting in closer twine spacing (a greater number of twine wraps around the bale) than is desired as the twine arm approaches a position generally parallel to the bale length. Furthermore, it may be desirable to alter the twine spacing for different crop materials. Variations in the rate at which the twine arm sweeps through its arcuate path or the rate of bale rotation result in non-uniform twine spacing along the bale as the separation between the two strands being dispensed does not vary. These conditions comprise the efficiency with which the bale can be wrapped.
In an effort to overcome these limitations, assignee's U.S. Pat. No. 6,769,353 to Smith et al., discloses an improved twine wrapping apparatus comprising four twine tubes on two twine dispensing arms to facilitate the rapid wrapping of a formed bale. Each twine dispensing arms comprises a pair of parallel links terminating in a cam member that is necessary to maintain the twine tubes evenly spaced apart and directing twine perpendicular to the bale axis throughout movement of the dispensing arm. The physical size of this mechanism results in increases debris accumulation on the mechanism; its complexity generally increases production costs.
It would be desirable to provide a simplified mechanism for feeding four individual twine strands into a bale chamber for wrapping a bale that provides comparable bale wrapping results, enables user adjustment to optimize twine spacing (number of wraps on a bale) for various crop materials, minimizes debris accumulation on the mechanism, and reduces the time required to perform the wrapping operation. Still more desirable would be a twine feeding mechanism that is easily incorporated into existing round baler designs with minimal alteration of the bale forming and wrapping mechanisms.